(Copied from original User Voice forum)
"When 'unloading' a plugin, the .mll file is still locked by Maya. This is very annoying because when you want to make a quick fix to the plugin, it requires restarting Maya completely to build a new version of the plugin.
Explorer seems to be able to move the file, but Visual Studio cannot overwrite it.
Process Explorer by SysInternals shows maya.exe holding one handle to the plugin dll as a file and loading the dll twice. (?)"